Airtight Networks security researcher Bhupinder Misra dug into the MAC address randomization feature built into iOS 8. As Apple described it, the feature seems pretty good for users: When your device is searching for Wi-Fi, say in a mall or sports stadium, it will send out a randomized MAC address, rather than your phone's actual code. Ostensibly, this would prevent retailers from using your phone's MAC address to send you contextual advertisements based on your location within the reach of their Wi-Fi.

But there are caveats: Earlier this week, Misra discovered that on an iPhone 5S, the MAC randomization only happens when the phone is in sleep mode (i.e., display turned off) with Location services turned off. If you wake up your iDevice to check a text message, or if you leave your GPS signal turned on to use navigation or a fitness tracking app, you're out of luck.

That's right; according to this research, if you don't want people tracking your iDevice, you've got to leave it in sleep mode, with GPS turned off, and disconnect your cellular data. If you've done all that, you'll be safe, sure. But at that point, you might as well have left your smartphone back at home, because there's absolutely no utility in carrying around a device that you cannot turn on. Unfortunately, as it stands right now, that's the only way you can utilize the randomized MAC address feature Apple says will prevent retailers from tracking you.